Hydraulic drive for hoists or the like



5 Sheets-Shegt 1 INVENTOR. F04 6 679n i x /LM J rney .R. E. GIGNOUX HYDRAULIC'DRIVE FOR HOISTS OR THE LIKE F lled Jan 1, 1945 Jan. 14, 1947.

Jan. 14, 1947.

R. E. GIGNOUX 4 ,197 HYDRAULIC DRIVE FOR HOISTS OR THE LIKE Filed Jan. 1, 1945 5 sheets-sheet 2 mmvron l?- M (f a a a X i WM Jan. 14, 1947. R. E. GIGNOUX I 2,414,197

HYDRAULIC DRIVE FOR HOISI'S OR THE LIKE Filed Jan. 1, 1945 s Sheets-Sheet s o 0 Q a 0/1 0 aT/ mmvron af noux J O F-uey Jan. 14, 1 947. oux 2,414,197

HYDRAULIC DRIVE FOR HCISTS OR'THE LIKE Filed Jan. 1, 1945 5 Sheets-Sheet 4 Armani 5r @Q'MM/ Jan. 14, 1947.- R, GIGN X 2,414,197

HYDRAULIC DRIVE FOR HOISTS OR THE LIKE Filed Jan. 1, 1945 5 Sheets-Sheet 5 a z: y wk J X H? 11 11: 2 4 o 2/0 J1" Z2 40 2Z0 1::

4 3a INVENTOR.

fra/ lr E 67 1 s me Jan. 14, 1947 UNITED STATE s .PATE

NT. omcs J HYDRAULIC muvs son HOISTS on 'rnnanm Ralph E. Gignoux, Bakersfield, pm., assignor to Hopper Machine Works, Inc., Bakersfield, Calm, a corporation of California Application January 1, 1945, Serial No. 570,987

' a (Cl. 60-53) v '1 This invention has to do with a drive for hoists,

. or the like, and it is a general object of the in- .ciflc type or form of hoist presenting a typical example is the hoist of a well drilling rig. Such a hoist involves, primarily. a hoisting drum which handles a line which operates through suitable blocks to handle tools or equipment at the well. The tools or equipment that must be handled vary widely as to weight, and their movements vary from static conditions at some times to rapid movement at other times. The weights and strains involved or imparted to the hoisting drum may vary gradually between wide limits, or may fluctuate continuously within reasonably narrow limits. As a result of the severe and varying operating conditions that must be met in such an apparatus it ha been common to provide such apparatus with heavy or powerful prime movers and the skilland judgment of the operator has 11 Claims.

operation for the prime mover and a governor which can be employed so the prime mover is maintained at a selected speed under varying load conditions. Through the control that I have provided for the prime mover the drive or system for the transmission of power from the prime mover to the work is supplied with a constant such as a constant volume or flow of actuating fluid, even though pressure of such fluid may vary. By thus controlling and governing the prime mover the operator is given adequate and efiective control over the action'oi the apparatus.

been relied upon to make the necessary adjustments or compensations. 'In'generai the conditions are such that little or no attempt has been made to effect economy of power or efllciency in operation, as little has been possible in that direction with the common type of equipment heretofore used. 1

In its preferred form my invention can be most advantageously applied to the hoist or a well drilling rig. when I employ the term hoist and when I refer to a hoisting drum I mean to include and I refer to a mechanism or work element presenting the problems or general characteristics of a hoist or hoisting drum.

It is a general objectv of my present invention toprovide a drive for a hoist which is a complete system of power generation and transmission involving the operation of the hoistfrom a prime mover which preferably involves a plurality of independently operating units. The

narily varies or adjusts itself to load conditions so that it supplies the force necessary to handle present invention provides a drive which ordi- Another object of my invention is to provide a drive of the general character referred to in which fluid is employed as the power transmitting medium and in which the fluid is employed to drive a motor which is governed so that its speed of operation automatically varies according to the load or torque conditions. With the mechanism of the present invention fluid supplied by the action of a pump driven by the prime mover at a. constant volume acts in the motor so that pressure is developed in the fluid up to the maximum available from the prime mover, and pump, and the speed of operation of the motor then varies in proportion to the load or the work imposed on it, so that the work is handled at the maximum speed possible with the power supplied under the set condition of the prime mover and pu p.

Another object of the present inventionis to provide a hydraulic system or drive of the general character hereinabove referred to in which the fluid is handled in a closed circuit and a high pressure means'is provided for supplying any leakage or loss of fluid that may occur in the system.

It is another object of my present invention to provide apparatus of the general character hereinabove referred to, in which there are variable displaeement fluid pumps which make it possible for the operator to vary the speed oi the driven fluid motors by varying displacement of the pumps while maintaining a constant or substantially constant pressure condition in the system. The apparatus is such that with constant pressures if volume is decreased the torque will increase proportionately.

An important object of my invention is to pro-' devices and which is a common source of trouble and is inconvenient-and slow to operate. I acomplish full control in both directions oi operof parts shown in Fig. 1.

ation without at any time disconnecting the prime mover from'the work as occurs with a clutched drive.

Another object of the invention is to provide a hydraulic system of the general character hereinabove referred to in which the relief valve or pressure relief is provided so that regardless of the setting or operation of the prime mover or of the load or torque imposed at the work the system can never be loaded beyond a given pressure. With the drive of the present invention pressure develops adequate to handle the work and the work is moved at a speed maximum for the pressure available, but if the load is excessive or greater than the drive can handle safely, the drive will not fail but will simply not move the work.

Another object of my invention is to provide a drive of the general character referred to involving multiple units, as for example, two independent prime movers and pumps operated thereby, and two work-handling motors with automatic controls therefor, and a master control whereby both the motors can be driven-from fluid supplied by both of the pumps or either or both of the motors can be driven from either of the pumps, but under no conditions can but one of the motors be driven from both of the pumps.

By this control the apparatusis sale and dependable in that it is not subject to shut down because of failure of a prime mover, a pump, or a motor, and it is safe against the motors being driven at excessive speeds. 'In practice the elements are related or balanced as to capacity so that the motors are operated at maximumsafe capacity when powered from the two prime movers. By making it impossible to supply the power from both prime movers to but one motor I eliminate the danger of overspeeding of the motors.

The various objects and features of my invention will be understood from the following detailed description of a typical preferred form and application of the invention, throughout which description reference is made to the accompanying drawings, in which:

Fig. 1 is a side elevation of a typical installation involving the drive of the present invention showing a power driven hoist for use in handling well apparatus. Fig. 1A is a sectional view of a servo unit that may be used in the control provided by the invention. Fig. 2 is an enlarged plan view of a part of the mechanism shown in Fig. 1, being a view taken substantially as indicated by line 2- -2 on Fig. 1. Fig. 3 is a view taken substantially as indicated by line 3-3 on Fig. 2. Fig. 4 is an enlarged view Fig. 5 is a diagrammatic view illustrating the drive provided by my invention. Fig. 6 is a sectional view of the control used in carrying out my invention. Fig. 7 is a sectional view taken substantially as indicated by line '!I on Fig. 6, and Fig. 8 is a sectional view taken on line 8-4! on Fi 7.

The drive of my present invention provides one or more prime movers for operating a work unit such as the hoisting drum of a well drilling rig, or the like. In the particular form of the inpumps being piston type positive displacement vention shown in the drawings I have illustrated I an arrangement wherein there are two prime movers and a single hoisting drum. In this case the prime movers A are indicated as internal combustion engines and the hoisting drum B is 4 a simple line-handling drum supported on a shaft it.

The mechanism oi my present invention, that is, the drive and control that I have provided between the prime movers A and the drum B,

involves, generally, a control C for the prime movers, a pump D operated by each prime mover, a control E for the pumps, a single operator F for the controls C and E, motors G connected to drive the drum and operated by fluid from the pumps, automatic controls H for the motors and a master control I for the actuating fluid supplied to the motors by the pumps.

The prime movers A may be of any suitable form such as electric motors or engines. In the case illustrated I have indicated internal combustion engines. The two prime movers may be mounted and operated independently of each other except insofar as they are connected by means of the control means C, as hereinafter described.

The control means C shown in the diagram involves, generally, a mechanism connecting the operator F with the prime movers or engines sothat they can be set to operating at any desired or selected speed. For example, if the engines are of the gasoline type the carburetors or throttles can be set through the means C from the operator F so that the engines have a given speed of operation.

It will be apparent that various mechanical arrangements may be employed between the operator F and the throttles of the engine to accomplish the function Just described. In the case illustrated the operator F includes a hand wheel ll fixed on a shaft I2 which is both rotatable and shiftable axially. The means C involves a gear l3 slidably keyed to the shaft I2 and suitable gearing and shafting connecting the gear l3 with the engine throttles.

In the case shown in the diagram Fig. 5, the gear l3 meshes with and drives a complementary gear l4 on a shaft IS. A shaft 18 extends between the engines and is driven from the shaft it: through meshing gears II. There is a shaft it at each engine driven from the shaft l6 through gears it. Through the arrangement just described rotation of the shaft 52 will operate the shafts I8 to move the engine throttles' The control C includes, in addition to the mechanism above described, governors 2a which may be employed to operate independently to hold or maintain the engine speed as the load or resistance varies. Each engine has a speed governor 28 which may be set to hold the engine at the desired speed.

I have shown details of the means C in Fig, 5,

but have omitted them from the other figures application of my invention I employ pumps commonly known as wobble plate pumps, such pumps in which there is a wobble plate or variable element under control of a part such as a lever arm or line element 2|. In this type of pump when the wobble plate or its corresponding element is in one position, for instance, a neutral position, the pump will operate withoutcreating any pressure or displacing any fluid. As the wobble plate is varied or deflected from such.

neutral position displacement increases causing increased flow or volume. The pressure developed by the pump will build up as resistance is encountered until it reaches maximum for-the unit or the setting of the apparatus. By employing wobble plate type pumps the operator can set the pumps to deliver any desired volume of fluid within the capacity of the pumps and as resistance is encountered the pressure will build up until it reaches maximum for the pumps, or the pressure at which the safety means is set, whichever ls the. lowest. I

The means E for controlling the pumps or varying their action operates to vary the position of the wobble plates through operation of the levers 2!. In the case illustrated the variation or'ach'ustment of the pumps is effected through axial shifting of the shaft l2. This motion is communicated to the levers 2| of the pumps by links 22 and rods 23 which operate servomotor units 28 connected to the levers 21 by rods 25. The servomotors are operated by fluid under pressure from pumps L50 driven from the engines and which operate to maintain fluid under pressure in a supply line I51. Lines ISle connect line t5! with the servomotors. A pressure governing valve 452. allows excess fluid from pumps 850 to return to the reservoir l53. In practice a system of drainage connections may be provided so that whenever there is slippage or leakage of fluid that fiuidis returned to the reservoir 553.

Each servomotor may involve or include a cylinder lfi l which is held in a fixed position, a piston E55 operable in the cylinder I54 and connected to the shiftable element of the pump D, as through a suitable rod 25, and a valve member i556 operable in a valve chamber l5! provided within the piston I55. Fluid under pressure is maintained in the space M8 at one end of the piston and when the device is in the neutral position fluid is trapped in the space I59 at the other end of the piston. When the valve I56 is moved to the right a port l 60 in communication with space it?! is put in communication with a port iti in the valve which allows the fluid to escape to a chamber H65 at the end of the valve so the pressure in chamber 558 moves the piston H55 until the said ports are cut ofi or closed. When the valve lsmoved to the left port I'll), which communicates with space 956, is put in communication with port lfill so fluid pressure develops in space I59} The effective area of piston Hi5 at space I59 is greater than that at space W8 so the piston W5 is moved to the left until the ports. lit and-Mil are cut off.

The motors G operatively connected with the drum B, as by chain drives 26, or the like, are preferably mechanisms corresponding, generally, to the pumps, that is, they are positive displacement variable motors of capacities substantially equal to the capacities of the pumps. In the particular form illustrated in the drawings where wobble plate pumps are used, I employ wobble plate motors G- and the wobble plate of each motor is under control of a control member 30. As the wobble plates of the motors are in aneutral position there will be no flow through them and no rotation. As the plates are deflected or movedirom the neutral position flow will occur through the motors and as the deflection increases the speed decreases or the amount of fluid passed per revolution increases. In practice the units are not set to have a completely neutral position but rather have a minimum displacement when in the position thatI refer to as "neutral." It will be understood, or course, that when the speed of rotation of the motors is slight. maximum torque may develop so that the torque delivered is high, whereas as the speed increases the torque will decrease, due to changein position of the wobble plates while pressure may remain constant.

In accordance with my invention the pumps D and the motors G are connected by suitable fluid lines or conduits and the master control I. .In the preferred arrangement a line 40 connects each pump with master control I. Lines 42 connect the 'control I with the motors G'. Motors G are connected to the pumps D by lines 43 and lines 43 connect the control I with the'pumps D. When the mechanism is operating in one direction, which I will call the forward direction, the lines it deliver fluid under pressure from the pumps D to the control I and the lines 42 conduct fluid under pressure from the control I to the motors G. In this case the lines d3 conduct fluid from the motors G to the control I and the lines 413 conduct fluid from the control I back to the pumps D. When the mechanism is operating in reverse or in the opposite direction the flow in the system is opposite to that just described, and

fluid is delivered by the pumps D under pressure through the lines ls to the control I, and the lines at conduct fluid under pressure from the control I to the motors G. In this case lines d2 conduct fluid from the motors G back to the control I and lines to conduct fluid from the control I back to the pumps D.

My present invention provides a safety or relief means which governs the pressure that can develop in the system. This means may be incorporated in the control I as I will later describe.

The automatic control means H provided by my invention involves a, construction whereby the control members 36 of the motors are operated or varied in response to the pressuredeveloped in the fluid operating the motors. This pressure may be taken off at any suitable point in the system. In the particular case illustrated control pressure lines 5d are taken off of the lines at and 33 and, connect with the cylinders St to act'on pistons 52 in the cylinders. Pressure operated valves 5U in lines 58 act to allow high pressure to enter the cylinders 5i and are only opened by pressure greater than that on the low pressure mum deflected positions. In such minimum deflected positions the wobble plates cause the motors to operate "at a maximum speed. As pressure develops in the operating system between the p ps and the motors as a result of resistance to movement of the motors due to load on the drum B that pressure is communicated through the pressure connections 50 and valves 5!! so that the pistons 52 are moved against the resistance of the springs 53, thus causing the wobble plates to be moved toward the full capacity positions from their neutral positions; When the pressure decreases valve til will be held open so long as the pressure is above a given amount and the spring will act to return the piston 52 displacing fluid from cylinder 5| through the open. valve.

The master control I may vary widely in construction and formation. In the form of the invention illustrated the master control involves, generally, a body M containing various chambers and ports and carrying check valves and control valves by which the pressures involved are sublect to control. In general the lines 40 and 43 7 connect into thetop of the body-4| while the lines 42 and 43 connect into the bottom of the body. Two main chambers 200 and 20! extend parallel to eachother in the body 4|. Each line 40 connected into the top f the body is joined to chamber 200 by a port 202, each line 42 connected into the bottom of the body is joined to chamber 200by a port 203, each line 43 connected into the top of the body is connected to the chamber 201 by a port 204, and each line 13 .connected into the bottom of the bodyis con- ,nected with chamber 20l byaport 205.

Two valve members are arranged transversely in the body 4! or in valve chambers which are transverse of the chambers 200' and 201 and extend between the chambers 200 and 2M. One valve member controls one port 202 and one port 204 while the other valve member controls the other port 202 and the other port 204. The stems 2i0 of the valve members carry valve bodies 2 which control the ports 202 and valve bodies 2l6 which control the ports 2M.

Passages or ports 2i? join related ports 202 and 205 through or under control of valve 2i0. Each port 2 I is normally closed adjacent port 205 by a valve body 2 I 6 while the valve bodies 26 i and 2 It are normally positioned so that the ports 202 and 204 are open. If the valve member is moved from the neutral position so valve body 2! i closes port 202 while valve body 2; closes off port 204,

then the passage or port M5; is opened forming a'by-pass connection between the ports 202 and 205. Under this positioning of parts ports 2% and NI are cut off from port 2115 so there is no return from the motorthrough'ports 28 3 or 2M to port 205. At the same time the spaced parts of port 2l5. are connected by the valve 2") so flowcan occur through ports 202, 2l5, 205 and 513 back to the intake of the pump. Assuming that the apparatus is being operated in the normal or forward direction, fluid under pressure from the pumps enters the ports 202. If it is desired to disconnect one of the pumps the valve controlling the port 282 served by that pump is closed by moving the valve member out or in the direction indicated by the arrow X in Fig. 6, with the result that the fluid from that pump instead of entering the chamber 200 goes through the by-pass 2 i 5 into port 205 which is handling the exhaust fluid.

During such setting the other valve may be left as shown in Fig. 6, so that fluid from the other pump is distributed to the two motors G and is exhausted into the chamber 20! through the connections 33 to return to the pumps D through the ports 205 and connections d3. Both lines 32 are always connected with chamber 200 and both lines d3 are always connected to chamber 205,

Each of the high pressure relief valves H d 223 is normally held closed by a sprin 11 has a piston 226 associated with it so that wh n pressure in the chamber which itcontrols exceeds a certain value the valve opens allowingfluid to escape from-that chamber into the by-pa s s'220 i from which it readilyescapes through the 103W, pressure check valve 222 or 224 into the low -pi -es--' sure side of the system. By providing twoby-pass ports 220 and relating the low pressure and pressure valves to these ports oppo'sitely,as shown in F g. 6, the system has eflective relief means regardless of the direction "of flow through the.-.

system.-.

' In accordance with the preferred arrangement 0 l the make-up feed or the fluid supplied to make up any leakage in the system is supplied from the line -l5l through connections lfil which connect into the by-pass ports 22.0 between the high and low pressure valves. Through this arrangement make-up fluid pressure is always maintained in' the by-pass ports 220' and regardless of which way the fluid is being circulated through the apparatus the necessary make-up fluid will be introduced into the circuit or system past one o! the low pressure valves. For example, if the system is being operated in thenormal direction so that there is high pressure fluid in chamber 200 then the high pressure .fiuid will hold the low pressure valve 224 at the top of Fig. 6 closed, but

will open the low pressure valve 222 at the bottom of Fig. 6, allowing make-up fluid'to enter chamber 20! so it enters thepumps D through the lines t3 which connect with chamber 20L The operation of the drive, as hereinabove described, is substantially as follows: The'operator so the output from both pumps can never be fed to only one motor. The cut-out action just described will occur when the mechanism is operated as described, regardless of the direction in which the fluid is circulating in the system.

In accordance with the preferred arrangement v a pressure relief means is provided to prevent through the single manual operator F may set the engines or prime movers operating at a predetermined or selected speed, and he sets the output or potential of the pumps at the desired point. The operator may set the engines at an idling speed or at a maximum speed where they will 0 develop a maximum amount of power, and he may set the pumps D to deliver a very small amount of fluid at the maximum pressure determined by the relief valve, or he may set them to deliver a maximum amount of fluid at a lower pressure. In other words, the operator sets the valves or essential factors of the apparatus and then the apparatus operates so that the load or torque encountered determines the pressure developed up to the maximum for the apparatus or as set bythe relief means. For any given setting of the prime movers and pumps a given amount of fluid will be delivered by the pumps with a certain pressure potential or possible pressure. This fluid is handled or passed through the master control to the motors G. Assuming a load to be on the drum B pressure immediately develops ,in the motors and connections 42 and consequently in the master control valve. This pressure is communicated by the connections to the cylinders 5| and consequently the wobble plates of the motors are immediately moved to a position where the pressure is sumcient to cause movement of the motors and consequent lifting or movement of the load. The position taken by the motors is determined by the torque and varies as-the torque varies, so that the apparatus operates at full capacity. If the load is greater than the drive will handle, the motors will not move but the fluid will simply be by-passed through the relief means in control I.

Whenthe load has once been started in motion it, of course,--will vary from a, static load to a prime movers. two reversible pump kinetic load or, as load condition may circumstances. As such variables occur the resistance or pressure in the hydraulic system will change and the means H-will act to automatically vary or regulate the wobble plates of the motors so that the speed of the motors is automatically varied to keep the motors operating to handle load as fast as possible under the volume and pressure being supplied by the pumps. 11 under a given motor setting and pump setting the drive is not suflicient to pickup or move the load the operator can either increase the speed oi the motors and thus deliver more power by reason oi a greater volume. or he may vary the setting of the pumps to deliver a smallervolume at a higher pressure, or he may tighten the relief. These factors being variable the operator has 9 the mechanism operates. the I vary due to many factors or considerable latitude in setting the drive to op-- erate in the most satisfactory manner. For max-- imum operating torque the prime movers would be set at full operating speed and the pumps would be set to deliver a maximum volume up to the maximum pressure set by the relief valve. If high torque is not desired under such conditions, but maximum speed is desired, the pumps would be set at maximum volume, in which case a substantial pressure would be obtained and also a. maximum volume would be obtained.

Having described only a typical preferred form and application or my invention, I do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any variations or modifications that may appear to those skilled in the art or fall within the scope of the following claims. I

- Having described my invention, I claim:

1. A drive for a hoisting drum including, two prime movers, two variable positive displacement pumps, one operated by each prime mover, two variable motors having driving connection with the drum, and a control including connections whereby fluid from both pumps is delivered to both motors and a valve controlling the flow from each pump so it can be cut on without stopping operation of both motors by fluid from the other pump.

2. A drive for a hoisting drum including, two positive displacement prime movers, two'variable pumps one operated by each prime mover, two

variable motors having driving connection with the drum, and a control including connections whereby fluid from both motors, individual independently operable valves controlling the fluid delivered by the pumps whereby the flow from either pump can be bypassed without going to the motors.

3. A drive for a hoisting drum including, two variable positive displacement one operated by each prime mover, two variable reversible motors having driving connection with the drum, and a control including connections whereby fluid from both pumps is delivered to both motors and a valve controlling the flow from each pump so it can be cut oil without stopping operation of both motors by fluid from the other pump.

4. A drive for prime movers. two variable positive displacement Pumps one operated by each prime mover and each having a control, means for varying the pumps including a manually operable member and servomotors operatively connecting the said member and the controls of the pumps, two variable motors having driving connection with the both pumps is delivered to the unit and fluid by fluid from both pumps is delivered to both motors and a valve controlling the flow from each pump so it can be cut oil without stopping operation of both motors by fluid from the other pump.

-5. A drive for a hoisting drum including, two prime movers, two variablepositive displacement pumps one operated by each prime mover and each having a control, means for varying the pumps including fluid pressure generating means operated by the prime movers, a manually operable member, and servomotors member and the pump controls fluid from the said generating able motors having driving connection with the drum, and a control including connections whereby fluid from both pumps is delivered to both motors and a valve controlling the flow from each pump so it can be cut on without stopping opera-. tion of both motors by fluid from the other pump.

6. A drive for a hoisting drum including, two prime movers, two variable positive displacement pumps oneoperated by each prime mover, means for simultaneously controlling the prime movers and for varying the having driving connection with the drum. and a control including connections whereby fluid from both pumps is delivered to both motors and a valve controlling the flow from each pump so it can be cut off without stopping operation of both motors by fluid from the other pump.

7. A drive for a hoisting drum including, two

delivered to both motors and a valve controlling the flow from each pump so it can be cut oi! without stopping operation of both motors: by fluid from the other pump.

8. A drive for a hoisting drum including two prime movers, two variable reversiblepositive displacement pumps, one operated by each prime mover, two variable reversible motors operatably connected to the drum, a control unit, fluid connections between each side of ,each pump and connections between each side of each motor and the unit, the unit including two separate chambers one having connections from only one side of each pump connected thereto and connections fromonly one side of each motor connected thereto and the other having only connections from only the other side of each pump connected thereto and connections from only the other side v thereto.

a, hoisting drum including, two

9. A driv for a hoisting drum including two prime movers; two variable reversible positive displacement pumps, one operated by each mover, two variable reversible motors operatably connected to the drum, a control unit, fluid connections 'between each side oi! each pump and the unit and fluid connections between each side of each motor and the unit, the unit including two separate chambers one having connections from only one side of each pump connected thereto and connections from only one side 01' each motor connected thereto and the other having only connections from only the'other side of each pumps, two variable motors of each motor connected prime um connected thereto and connections from only the other side of each motor connected thereto, the unit having valve controlled bypasse whereby fluid from either pump to either chamber can be bypassed to the other chamber. a)

' mover, two variable reversible motors operably 10. A drive for a hoisting drum including two prime movers, two variable reversible positive displacement pumps, one operated by each prime mover, two variable reversiblemotors operatably.

connected to the drum, a control unit, fluid con: 10

twoseparate-chambers one having connections nections between each side of each pump and the unit and fluid connections between each side of each motor and the unit, the unit including two separate chambers one having connections from only one side of each pump connected there- 15 to and connections from only one side 01 each motor connected thereto and the other having only connections from only the other side of each pump connected thereto and connections from only the other sideot each motor connected 20 thereto, the unit having bypasses between the chambers and oppositely arranged pressure regulating valves controlling the bypasses so fluid 12 1 at excess pressure in either chamber is bypassed to the other chamber.

11. A drive for a hoisting drumincludins two prime movers, two variable reversible positive displacement pumps, one operated by each prime connected to the drum, a control .unit. fluid connections between. each side of each pump and the unit and fluid connections between each side of each motor and the unit, the unit including from only one side oi each pump connected thereto and connectons from only one side or each motor connected thereto and the other having only connections from only the other side 01 each pump connected thereto and connections from only the other side of each motor connected thereto, the unit having manually operated valve controlled bypasses whereby fluid from either pump to either chamber can be constantly bypassed to the other chamber.

" amn E. arcmonx.

Disclaimer 2,414,197.-Ralph E. Gignoux, Bakersfield, Calif. HYDRAULIC DRIVE FOR HOISTS OR THE LIKE. Patent dated Jan. 14, 1947. Disclaimer filed Aug. 18, 1948, by the inventor; the assignee, Vickers Incorporated, assenting. Hereby enters this disclaimer to claims 2, 8, 9, 10, and 11.

[Ofiicial Gazette September 14, 1.948.] 

